The use of intravascular medical devices has become an effective method for treating many types of vascular disease. In general, a suitable intravascular device is inserted into the vascular system of the patient and navigated through the vasculature to a desired target site. Using this method, virtually any target site in the patient's vascular system may be accessed, including the coronary, cerebral, and peripheral vasculature.
Medical implants, such as stents, stent grafts, flow-diverters, and vena cava filters, are often utilized in combination with a delivery device for placement at a desired location within the body. For example, with reference to FIG. 1, a medical implant 1, such as a stent, may be loaded into a delivery sheath 2 via a stent delivery mechanism 3. The stent delivery mechanism 3 comprises a delivery wire 4 having a distal tip 5 on which the stent 1 is affixed. The stent delivery mechanism 3 further comprises a proximal bumper 6a and a distal bumper 6b between which there is formed an annular channel 7 for engaging the stent 1 in a manner that allows the stent 1 to be axially displaced within the delivery sheath 2, while releasing the stent 1 once it is deployed outside of, and therefore no longer contained by, the delivery sheath 2. In this embodiment, the stent 1 includes one or more proximal radiopaque marker 8a (two shown) and one or more distal radiopaque markers 8b (two shown). The proximal radiopaque markers 8a reside within the annular channel 7 between the bumpers 6a, 6b to facilitate engagement between the stent 1 and the stent delivery mechanism 3.
The delivery sheath 2, with the stent 1 in its reduced undeployed configuration, may be introduced into the lumen of a blood vessel 9, and delivered to a target location within the blood vessel 9, as illustrated in FIG. 2A. Once delivered to a target location within the body, the stent 1 may then be deployed out of the delivery sheath 2 via the stent delivery mechanism 3 by retracting the delivery sheath 2 in the proximal direction, and expanded to an enlarged configuration within the blood vessel 9 to support and reinforce the wall of the vessel 9, while maintaining the vessel 9 in an open, unobstructed condition, as illustrated in FIG. 2B. The stent 1 may be configured for being self-expanding, expanded by a stored potential radial force such as a balloon, or a combination of self-expanding and balloon-expanded.
Oftentimes, it is desirable to remove the delivery sheath 2 from the patient while the stent delivery mechanism 3 remains in the patient, re-cross the deployed stent 1 with the stent delivery mechanism 3, and guide another device (not shown) over the stent delivery mechanism 3 into engagement with the deployed stent 1. For example, the other device may be a balloon catheter that is expanded within the deployed stent 1 to either expand the stent 1 into contact with the wall of the vessel 9 if the stent is not self-expanding, or if the stent is self-expanding, to ensure that the stent is an opposing engagement with the wall of the vessel 9.
However, crossing the deployed stent 1 with a delivery wire 3 poses challenges due to mechanical interactions between a distal tip 5 and bumpers 6a, 6b of the stent delivery mechanism 3 and the struts of the deployed stent 1. As one example illustrated in FIG. 2C, the distal tip 5 of the delivery wire 4 may dig into the cells of the deployed stent 1, preventing reliable re-crossing of the deployed stent 1, especially when the stent 1 is deployed in a curvature of the vessel 9. Even if the distal tip 3 of the delivery wire 4 is re-crossed over the deployed stent 1, it is desirable to re-cross the deployed stent 1 a sufficient amount, such that the more rigid portion of the delivery wire 3 resides within the deployed stent 1 to facilitate delivery of the balloon catheter into the deployed stent 1. However, the forward edges of the bumper 6a, 6b, which are now exposed due to the removal of the stent 1, may catch on the struts of the stent 1, thereby creating additional challenges for re-crossing the deployed stent 1 a sufficient distance to allow the balloon catheter to be reliably guided into the deployed stent 1, as illustrated in FIG. 2D.